Guest Ubuntu visual effects don't work w/ dual screen

Description

Hi,

I'm running on my laptop, VB 3.0.0 on an XP host and I have an Ubuntu 9 guest.

When only one screen is connected to this laptop, all Ubuntu visual effects of my guest are working well. If I connect 2 screen, I'm only able to display visual effects when my VB windows is on my external screen (screen #1). If I put it on my laptop screen (screen #2) I got only a black window. More, if I move the windows from screen #1 (working) to screen #2, the VB guest window is not anymore refreshed.